1. Field of the Invention
The present invention relates to automatic audio detecting switching devices and more particularly, but not by way of limitation, to a mixing selector circuit having a micro-computer for the automatic fading and switching of a plurality of audio signals. The automatic switching selector device may be built into the amplifier and/or tuner or may be constructed as a black box which is connectable to the input and output jacks of existing sound systems.
2. History of the Prior Art
A typical home entertainment system comprises a tape deck, record player, AM/FM stereo tuner and amplifier and speakers. Often at parties or social events it is desirable to have background music which may consist of an FM radio station or records or both.
The constant monitoring of a record changer can become a nuisance to the host in changing records and turning on the FM station when the records are finished playing.
This problem not only exists in entertainment systems but also at commercial radio stations where it was desired to monitor a priority signal source.
If a disc jockey is away from his station when a record finishes playing, it would be desirable to automatically fade in or switch in an alternate signal source.
Several attempts have been made to solve this problem by rather elaborate programming devices such as taught in the patent to Smith, Sr., U.S. Pat. No. 3,809,812, issued in 1974 for a "Programming System". While such a device might be feasible for an unmanned FM station, it would be prohibitively expensive and complicated for home use.
A more pertinent solution to the problem was provided by two patents to Gates, U.S. Pat. No. 3,952,154, issued in 1976 for "Automatic Audio Source Selector For Stereo Entertainment Centers" and the subsequent patent, U.S. Pat. No. 3,956,591, issued in 1976 for "Two-Input Automatic Source Selector For Stereo Entertainment Centers".
While the two patents to Gates solved the basic problem set out above, the selection of audio in the Gates patents is by switching abruptly from one source to another when sound has been detected on the priority source. This solution to the problem could be more disconcerting than the problem itself and would give rise to switching back and forth during the pause between songs on a single record. Further, if a record or tape is the priority source, and switching is not made until the source is already playing, often the first notes of the musical composition are clipped and one does not hear the full record.